The present invention relates to a tool steel for warm and hot working which is especially high in warm and hot strengths and abrasion resistance and has excellent toughness and hardenability.
Metallic mold for warm forging and hot precision press forging is required to be especially excellent in hot or warm strength and abrasion resistance because of severe requirement for high accuracy in size of material to be molded. At present, AISI M2 (JIS SKH 9) which has an excellent toughness as high speed steel for cutting tool is used and AISI M35 (JIS SKH 55) which corresponds to said AISI M2 to which Co is added are used.
However for some uses, the AISI M2 alloys are not sufficient in abrasion resistance. The AISI M35 alloy is not sufficient in toughness and early heat cracks and large cracks sometime occur. Furthermore, for some uses, a toughness of higher than that of AISI M2 is required and when amount of carbon is decreased for this purpose, the abrasion resistance becomes insufficient. Thus, sufficient practical steel life has not been obtained.
Moreover, AISI M2 and M35 are low in hardenability and when they are used for metallic molds of middle-large size, their essential characteristics cannot be easily exhibited.